In a wind turbine, when a main shaft connected to blades for receiving a wind force rotates, rotation of the main shaft is accelerated by a speed increasing gear. By the accelerated rotation of the main shaft, a rotor of a power generator rotates to generate electric power. In order to diagnose the state of a wind turbine, vibration of the main shaft, the speed increasing gear, the power generator, and the like is measured by a vibration sensor.
A state monitoring system disclosed in PTD 1 (Japanese Patent Laying-Open No. 2013-185507) is constituted to include a current sensor or a vibration sensor attached inside a nacelle, a monitor device inside the nacelle, and a data server. The vibration sensor or the current sensor transmits a measured value to the monitor device by wireless communication. The monitor device transmits the measured value from the vibration sensor or the current sensor to the data server.
A portable vibration diagnosis device disclosed in PTD 2 (Japanese Patent Laying-Open No. 2012-98149) includes a plurality of vibration sensor units, and a vibration diagnosis unit that receives wireless signals transmitted from the vibration sensor units and diagnoses an apparatus.